relatime – A filesystem mount with this option causes the access time to be updated if they are (before the update has occurred) earlier than the modification time. This significantly cuts down the writes caused by atime updates.

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To improve performance, most users would want to add the noatime mount option, which results in a faster system since access times aren't registered (you don't need those generally anyway). This is also recommended for solid state drive (SSD) users, who should also enable the discard mount option (ext4 and btrfs only for now) which makes the TRIM command work.

atime option updates the atime of the files every time they are accessed
noatime option fully disables writing file access times to the drive every time you read a file.
relatime enables the writing of file access times only when the file is being modified

Il wiki riguardo ad atime dice anche:

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This is more purposeful when Linux is used for servers; it does not have much value for desktop use

Some users don't want their /boot partition to be mounted automatically to improve their system's security. Those people should substitute defaults with noauto. This does mean that you need to manually mount this partition every time you want to use it.